Gobbling Google: The search giant's biggest acquisitions (pictures)

With Google's recent purchase of Nest, we look at other big buys that have expanded Google's footprint way beyond the search engine.

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Nest

Google's purchase of the smart home company Nest (and its smart thermostat, pictured above), generated a lot of buzz on January 13, 2014. The tech titan has acquired more than 100 companies over the years. Not all of them were quite as expensive as Google's latest purchase, which cost the company $3.2 billion, but that doesn't mean the rewards weren't huge. We take a look back at some of Google's biggest purchases.

Android

This was a definite win for Google. Once an under-the-radar startup in Palo Alto, Calif., Android is now the namesake of the world's most popular mobile operating system. Google quietly purchased the then little-known company in 2005 for an estimated $50 million. Five years later the operating system was on 33 percent of smartphones, prompting Google to call Android the "best deal ever." That rings even more true today; the Android operating system powers more than 80 percent of smartphones worldwide.

YouTube

Google spent $1.65 billion for video-sharing service YouTube in 2006, just as the service was picking up steam. The company was already a hot item. Google reportedly beat out the likes of Microsoft, Yahoo, and News Corp. to get YouTube, which at the time hosted 100 million videos and drew 20 million unique visitors a month. These figures pale in comparison to YouTube's numbers today: 1 billion unique monthly visitors now watch more than 6 billion hours of videos every month. The service has even fulfilled Google co-founders Sergey Brin's earlier vision as an aggressive advertising platform.

Motorola Mobility

Motorola gave Google the resources to get into smartphone manufacturing while also delivering valuable patents for wireless technologies. Those same patents were a lightning rod for patent lawsuits, and a recent ruling went in favor of Google's rival, Apple.

Boston Dynamics

This recent purchase -- along with the acquisition of a slew of similar companies around the same time -- show Google's commitment to robotics. Google bought Boston Dynamics in December 2013 for an unknown sum. The robotics company rose to Internet fame for its animal-inspired robots, including Cheetah, BigDog, WildCat. The company's YouTube videos show these mainly gas-powered robots leaping through ice, snow and other obstacles. Many of Boston Dynamic's creations were funded by the U.S. Department of Defense's Defense Advanced Research Projects Agency.

Zagat

Google acquired Zagat in 2011, paying $151 million to purchase the restaurant-rating company. The deal, which added reviews of establishments in more than 100 cities, was meant to boost Google's local business listings. Google integrated Zagat's reviews into its widely-used Google Maps service, so when people are searching for locations, they can see businesses as well. The company recently overhauled the service, updating the site, introducing new iOS and Android apps, and making it free to access the directory. Unfortunately for Google, it still hasn't been able to compete with Yelp, which is at the moment is conquering this market.

AdMob

Similar to DoubleClick, the purchase of AdMob in 2009 was meant to bolster Google's advertising offerings. Google paid $750 million for AdMob, which specialized in mobile advertising, or more specifically, placing ads on Android phones. The service has helped Google grow its mobile advertising dollars -- an increasingly important task now that users have moved onto mobile devices for their everyday needs.